As shown in FIG. 1. The prior art provides a driving circuit, comprising a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4 and an input voltage source V1. An anode of the first diode D1 is employed for inputting a voltage VAA, and a cathode of the first diode D1 is coupled to an anode of the second diode D2, and a cathode of the second diode D2 is coupled to an anode of the third diode D3, and a cathode of the third diode D3 is coupled to an anode of the fourth diode D4, and a cathode of the fourth diode D4 is employed for outputting the voltage VGH, and the first end of the first capacitor C1 is coupled to a common end of the first diode D1 and the second diode D2, and the second end of the first capacitor C1 is coupled to a first end of the input voltage source V1, and a second end of the input voltage source V1 is grounded, and a first end of the second capacitor C2 is coupled to a common end of the second diode D2 and the third diode D3, and the other end of the second capacitor C2 is grounded, and a first end of the third capacitor C3 is coupled to a common end of third diode D3 and the fourth diode D4, and a second end of the third capacitor C3 is coupled to the first end of the input voltage source V1, and a first end of the fourth capacitor C4 is coupled to a cathode of the fourth diode D4, and a second end of the fourth capacitor C4 is grounded. In ideal condition, the relationship between the input voltage VAA and the output voltage VGH is: VGH=VAA+2*V1.
In practical application, for convenience, one output line of the power supply management chip PWM IC is employed to be the input voltage VAA, and the driving signal LX1 in the BOOST line generating the VAA voltage in the power supply management chip is the input voltage source, and is coupled to a resistor in series for obtaining the driving circuit shown in FIG. 2. Then, the relationship between the input voltage VAA and the output voltage VGH is: VGH=VAA+2*LX1.
However, in such arrangement, if the loading of the input voltage VAA is lower or the change of the loading is larger, the power supply management chip PWM IC will enter the DCM mode. The DCM mode is the Discontinuous Conduction mode. In the DCM mode, the ripple wave of the driving signal LX1 is very large and results in that the ripple wave of the output voltage VGH is very large, too.